Transformer tap-changing apparatus



July 30, 1935. L. F. BLUME TRANSFORMER TAP CHANGING APPARATUS Filed Nov.1, 1934 ow W. mn m eF ct We W 1% B LW Patented July 30, 1935 UNITEDSTATES PATENT OFFICE TRANSFORMER TAP-CHANGING APPARATUS Louis F. Blume.Pittsfield, Mass, assignor to General Electric Company, a corporation ofNew York Application November 1, 1934, Serial No. 750,953

/ 4 Claims. (ili. 171 119) My invention relates to transformer tap-changanother circuit 2i and rotate the motor to in ing apparatus and moreparticularly to that type the other direction if the voltage of thecircuit l t of apparatus in which energy is stored in a spring decreasesbelow normal. The motor to is con or equivalent device in response to avariation nected through a set of reducing gears 22 to a from a desirednormal voltage of a circuit, the shaft 23 which drives a disk. 2%provided with a 5 energy being subsequently automatically released cam25 and a pin 26. A second shaft in alignto change the tap connection ofa transformer to ment with the shaft 23 is provided with a disk 28restore the circuit voltage to normal. The genwith a pin 29 and aperipheral projection 35. The era! object of the invention is to providemeans shaft 2'l is arranged to operate the movable conw' for preventinginjury to such apparatus in case tact it of the switch i4 through aGeneva type it fails to function normally. gear 3t having a slotted disk32 and a driving The invention will be better understood from pin 38.The w p n 8 d project w n the following description taken in connectionwith the two outwardly turned ends 8d and 35 of a. the accompanyingdrawing in which Fig. 1 shows sp g 36 o d about the Shaft The Spring mytransformer tap-changing apparatus of the type it is under tension sothat its two ends 34 and referred to with protective means arranged intend to hold the pins 26 and 29 together as accordance with theinvention, and Fig. 2 is an shown in Fig. 2. explanatory View of a partof the apparatus. Assume now that the voltage of the circuit to Likereference characters indicate similar parts increases above its desirednormal value. The in both figures of the drawing. voltmeter to willclose the circuit 26 and cause The apparatus shown in the drawing isarthe motor is to rotate the shaft 23 in the direcranged to maintainsubstantially constant volttion of the arrow 3?. The shaft 23 will actage in a circuit til supplied. with voltage from the through the pin 6,t Spring 35 and the p 39 secondary winding it of a transformer 52. Theto rotate the shaft 2i slowly in the direction 25 transformer winding ii is provided with taps conof the arrow 31 until the projection strikesnected to the fixed. contacts 03 or" a switch it. A a spring-pressedstop 35 which will prevent fur two-part contact 95 of the switch M ismovable ther rotation of the shaft 2? and further movealong the fixedcontacts 13. One side of the cirment of the end 34% of the spring Theshaft wit it is connected to one end of the transformer 23, however,will. continue to rotate and act winding l i. The other side of thecircuit to is through the pin 26 on the end of the spring connecteddirectly to one part of the switch conto increase the tension of thespring and the tact it and through an impedance to to the pressure ofits end 3 3 on the pin thus storing other part of the switch contact is.The two n r y in h pring. The c m will finally parts of the switchcontact to are insulated from reach a pin 39 and lift the stop 33 torelease the 5 each other and are angularly displaced about a proje ionand th di k 2 A h wn in F 0 common shaft 8? to which they are secured.Both the proj cti n 8 d d are j about parts of the movable switchcontact 55 normally he e a fi P release the disk the rest upon the samefixed contact it. When they stored energy in the spring 36 is releasedand the are moved to an adjacent fixed contact each P s Of t e e 34 0fSpring 011 the p part of the movable contact i5 is momentarily 9 wilrotate the haft 2? V y rapidly about ogJeh -circuited while it isbetween the two fixed one-half a revolution until it is stopped when thecontacts, the other part at this time carrying the pin Str kes the t end o t e Sp 35 full load current. Midway of the travel of the and theend 34' of the Spr ng s pp by {6118 movable contact 55, two parts bridgethe two pin This motion of the shaft causes .15 fixed contacts, at whichtime the impedance to pin of the Geneva gear to drive the shaft preventsexcessive circulating current between he it one step and transfer themovable contact 55 two fixed contacts. Thus, the contact to may he ofthe switch to very rapidly to the next fixed moved from one fixedcontact iii to another withcontact 33 so as to reduce the voltageapplied to out interrupting t e cur t in the Circuit the circuit iii. ifthe voltage has been thus re-- do The switch it is controlled by areversible moduced to its normal value, the voltmeter 59 will tor iiiand a contact-making voltmeter iii. The open the circuit to and themotor is will stop. voltmeter it is connected across the circuit itOtherwise the motor it will continue to operate and is arranged to closeone circuit 20 and rotate until the normal voltage of the circuit to hasbeen the motor in one direction if the voltage of the restored. circuitto increases above normal and to close the voltage of the circuit itdecreases below its normal desired value, then the voltmeter l9 willclose the circuit 2! and rotate the motor 13 to turn the shaft 23 in thedirection opposite to that indicated by the arrow 31. This will rotateboth shafts 23 and 21 until the projection 33 of the disk 28 strikes asecond spring-pressed stop M to prevent further rotation of the shaft2i. The shaft 23 will, however, continue to rotate and act through thepin 26 to tension the spring 36 until the cam reaches a pin M on thestop AW. The cam 25 then lifts this stop 60 and releases the projection30 and the disk 28 to permit the spring 36 ,to turn the shaft 2'? veryrapidly about one half a revolution and transfer the movable contactsl5.of the switch Hi very rapidly to the next fixed contact l3, thusincreasing the voltage of -'the circuit it.

In accordance with the invention the operating circuit of the motor I8includes two contacts iZ which rest on a commutator 43 mounted on theshaft 21. This commutator 43 includes a conductive section 44 and anon-conductive or insulating section 45, the insulating section beingarranged to break the motor circuit while the shaft 21 and the switch Itare being rotated by the spring 36. Under all other conditions ofoperation the contacts 32 rest on the conductive section l i ofthecommutator and the motor circuit is thus closed between these'twocontacts. The motor IS, in response to a variation from normal value ofthe voltage of the circuit In, will rotate the shaft 23 rather slowlybut when the spring 36 has been fully tensioned and the shaft 21 isreleased the spring will very rapidly rotate the shaft 27. and operatethe switch it one step. -However, the apparatus may not always functionas intended because of some excessive friction, breakage of the spring36 or other abnormal condition. Thus, instead of moving very rapidlyfrom one fixed contact E3 to another, as intended, the movable contactl5 may move slowly or may stop when not in normal position on a fixedcontact I3. The motor I8, however, would continue to drive the shaft 23-:and this might cause damage to some part of the apparatus or it mightcause the movable contact l5 to continue to move slowly so as to resultin serious arcing and burning of the contacts. Just as soon, thecommutator 43 reaches the contacts 42, the motor driving circuit isbroken and the motor stops so that further damage to the apparatus iseffectively prevented. This insulating section 45 of course interruptsthe operating circuit of the motor each time that the switch I4 isoperated by the spring however, as the insulating section 55 of 36 butthe interruption of the motor circuit is so brief as to havesubstantially no effect upon the motor.

The invention provides very simple and eifective protection forautomatic transformer tapchanging apparatus. It has been explained bydescribing and illustrating a particular arrangement and applicationthereof but it will be ob vious that changes may be made withoutdeparting from the spirit of the invention and the scope of the appendedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

l. The combination with a transformer having a winding with taps and acircuit connected thereto, of a switch for "changing tap connections toadjust the voltage of said circuit, means responsive to voltage changesin said circuit for storing energy, means for automatically releasingthe stored energy to operate said switch, and means for interrupting theoperation of said en ergy storing means during operation of the switch.

' 2. The combination with a transformer having a winding with taps and acircuit connected thereto, of a switch for changing tap connections toadjust the voltage of said circuit, means responsive to voltage changesin said circuit for storing energy, means including a shaft foroperating said switch, means for automatically releas-y ing the storedenergy to operate said shaft, and

means controlled bysaid shaft for interrupting the operation of saidenergy storing means during operation of the switch.

3. The combination with a transformer having a winding with taps and acircuit connected thereto, of a switch for changing tap connections toadjust the voltage of said circuit, means in-'- cluding a motorresponsive to voltage changes in said circuit for storing energy, meansfor releasing the stored energy to operate said switch, and a circuitinterrupter controlled by said switch operating means for interruptingthe driving circuit of the motor during operation of the switch.

4. The combination with a transformer having a winding with taps and acircuit connected thereto, of a switch for changing tap connections toadjust the voltage of said circuit, means including a motor responsiveto voltage changes in said circuit for storing energy, means including ashaft for operating said switch, means for releasing the stored energyto rotate said shaft, contacts in the driving circuit of said motor, anda commutator controlled by said shaft for opening said contacts duringthe operation of the switch.

LOUIS F. BLUME.

